JP4654885B2 - Ultrasonic motor - Google Patents

Description

  The present invention relates to an ultrasonic motor, and more particularly to a motor that rotates a rotor in pressure contact with a stator.

In recent years, an ultrasonic motor for rotating a rotor using ultrasonic vibration has been proposed and put into practical use. This ultrasonic motor generates a traveling wave on the surface of a stator using a piezoelectric element and moves the rotor through a frictional force between the two by bringing the rotor into pressure contact with the stator.
For example, in Patent Document 1, the rotor is pressed against the stator by preloading the rotor with a spring through a bearing, and a driving voltage is applied to a plurality of piezoelectric element plates that are superposed on each other in this state. Discloses a multi-degree-of-freedom ultrasonic motor that rotates a rotor by generating ultrasonic vibration. Here, the preload refers to a pressure that presses the rotor against the stator at least without energizing the piezoelectric element.

JP 2004-312809 A

However, since the bearing is brought into contact with the rotor in order to apply the preload, there is a problem that the torque is reduced due to friction loss.
The present invention has been made to solve such a problem, and an object thereof is to provide an ultrasonic motor capable of realizing a high torque.

  An ultrasonic motor according to the present invention is disposed in a state in which the stator, a rotor that is contacted and supported by the stator, stator vibration means that vibrates the stator and rotates the rotor, and at least in contact with the surface of the rotor when stopped. A preload member and preload member vibrating means for pressurizing the rotor against the stator by vibrating the preload member are provided.

The preload member vibrating means may be configured to vibrate the preload member in a vibration mode different from the vibration mode of the stator to preload the rotor with respect to the stator.
The preload member can be elastically supported by the stator, and the stator vibration means can be configured to vibrate the preload member also as the preload member vibration means. In this case, the preload member may be supported by the stator via a spring.
Alternatively, the preload member can be disposed apart from the stator, and the piezoelectric element plate can be attached to the preload member as the preload member vibrating means. In this case, the preload member can be supported at a node position formed when vibrating by the piezoelectric element plate.

Note that a substantially spherical rotor may be used, and the rotor may be rotated about a plurality of axes by vibrating the stator by stator vibration means. In this case, a preload member having a ring shape arranged so as to surround the rotor in an annular shape along the circumferential direction thereof can be used.
Preferably, the preload member has an abutting member made of a low friction material at a portion where the preload member contacts the surface of the rotor. Further, the stator may be configured to contact the surface of the rotor only at a plurality of locations in the circumferential direction. At this time, it is desirable that the plurality of locations are symmetrical with respect to the rotor.
If the stator vibration means is composed of three pairs of piezoelectric element plates that generate vibrations in three different directions, a combined vibration in which at least two of the three directions of vibration are combined out of phase with each other is generated. Thus, an elliptical motion can be formed at the contact portion of the stator with the rotor.

  According to the present invention, an ultrasonic motor capable of realizing high torque can be obtained.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
1 and 2 show an ultrasonic motor according to Embodiment 1 of the present invention. A cylindrical vibrator 3 serving as a stator vibration means is sandwiched between the base block 1 and the stator 2, and the base block 1 and the stator 2 are connected to each other via a connecting bolt 4 passed through the vibrator 3. The entire ultrasonic motor has a substantially cylindrical outer shape. Here, for convenience of explanation, the central axis of the cylindrical outer shape from the base block 1 to the stator 2 is defined as the Z axis, and the X axis is perpendicular to the Z axis and the Z axis and the X axis are Assume that the Y-axis extends vertically.
The vibrator 3 includes first to third piezoelectric element portions 31 to 33 that are located on the XY plane and overlap each other, and these piezoelectric element portions 31 to 33 are insulating sheets 34. Are arranged in a state of being insulated from the stator 2 and the base block 1 through .about.37.

A concave portion 5 is formed on the stator 2 on the side opposite to the surface in contact with the vibrator 3, and a spherical rotor 6 is accommodated in the concave portion 5. The recess 5 includes a small-diameter portion 7 having an inner diameter smaller than the diameter of the rotor 6 and a large-diameter portion 8 having an inner diameter larger than the diameter of the rotor 6, and the boundary portion between the small-diameter portion 7 and the large-diameter portion 8 is XY. An annular step 9 located on the plane is formed.
Further, a ring-shaped preload member 11 is elastically connected to the upper portion of the stator 2 via an annular leaf spring 10 so as to be adjacent to the Z-axis direction. An annular corner 12 positioned on the XY plane is formed on the inner peripheral edge of the preload member 11, and the rotor 6 is held in contact with both the step 9 of the stator 2 and the corner 12 of the preload member 11, It is supported rotatably.

Here, the preload member 11 is urged in the direction of the stator 2 by the leaf spring 10, and the preload acts on the rotor 6 via the corner portion 12 of the preload member 11.
Further, since the leaf spring 10 is interposed between the stator 2 and the preload member 11, when vibration is generated in the stator 2 by the vibrator 3, the preload member 11 is in a vibration mode different from the vibration mode of the stator 2. It is configured to vibrate.

  For example, the base block 1, the stator 2, and the preload member 11 are each formed of geralumin, and the entire ultrasonic motor forms a substantially cylindrical body having a diameter of about 40 mm and a height of about 100 mm. As the rotor 6, a steel ball having a diameter of 25.8 mm is used.

  As shown in FIG. 3, the first piezoelectric element portion 31 of the vibrator 3 includes an electrode plate 31a, a piezoelectric element plate 31b, an electrode plate 31c, a piezoelectric element plate 31d, and an electrode plate 31e each having a disc shape. It has a superposed structure. Similarly, the second piezoelectric element portion 32 has a structure in which an electrode plate 32a, a piezoelectric element plate 32b, an electrode plate 32c, a piezoelectric element plate 32d, and an electrode plate 32e each having a disk shape are sequentially stacked. 3 has a structure in which an electrode plate 33a, a piezoelectric element plate 33b, an electrode plate 33c, a piezoelectric element plate 33d, and an electrode plate 33e each having a disk shape are sequentially stacked.

As shown in FIG. 4, the pair of piezoelectric element plates 31 b and 31 d of the first piezoelectric element portion 31 has portions that are divided into two in the Y-axis direction and have opposite polarities, and each has a Z-axis direction (thickness direction). The piezoelectric element plate 31b and the piezoelectric element plate 31d are disposed so as to be reversed with respect to each other.
The pair of piezoelectric element plates 32b and 32d of the second piezoelectric element portion 32 are polarized so as to be expanded or contracted in the Z-axis direction (thickness direction) as a whole without being divided into two. The element plate 32b and the piezoelectric element plate 32d are arranged inside out.
In the pair of piezoelectric element plates 33b and 33d of the third piezoelectric element portion 33, the portions divided into two in the X-axis direction have opposite polarities, and are opposite to expansion and contraction in the Z-axis direction (thickness direction), respectively. The piezoelectric element plate 33b and the piezoelectric element plate 33d are disposed so as to be reversed with respect to each other.

  As shown in FIGS. 1 and 3, the electrode plate 31 a and the electrode plate 31 e disposed on both surface portions of the first piezoelectric element portion 31 and the both surface portions of the second piezoelectric element portion 32 are disposed. The electrode plate 32a and the electrode plate 32e, and the electrode plate 33a and the electrode plate 33e disposed on both surface portions of the third piezoelectric element portion 33 are electrically grounded. In addition, the first terminal 31 t from the electrode plate 31 c disposed between the pair of piezoelectric element plates 31 b and 31 d of the first piezoelectric element portion 31 is connected to the pair of piezoelectric element plates 32 b of the second piezoelectric element portion 32. And the second terminal 32t from the electrode plate 32c disposed between the second and third electrode elements 32c and 32d to the third terminal from the electrode plate 33c disposed between the pair of piezoelectric element plates 33b and 33d of the third piezoelectric element portion 33. Terminals 33t are respectively drawn out.

Next, the operation of the ultrasonic motor according to the first embodiment will be described.
First, when an AC voltage having a frequency close to the natural frequency of the stator 2 is applied from the first terminal 31t to the vibrator 3, the pair of piezoelectric element plates 31b and 31d of the first piezoelectric element portion 31 is divided into two. The portion thus expanded alternately expands and contracts in the Z-axis direction, and generates flexural vibration in the Y-axis direction in the stator 2. Further, when an AC voltage having a frequency close to the natural frequency of the stator 2 is applied from the second terminal 32t, the pair of piezoelectric element plates 32b and 32d of the second piezoelectric element portion 32 repeatedly expands and contracts in the Z-axis direction. The stator 2 generates longitudinal vibration in the Z-axis direction. Further, when an AC voltage having a frequency close to the natural frequency of the stator 2 is applied from the third terminal 33t, the two divided portions of the pair of piezoelectric element plates 33b and 33d of the third piezoelectric element portion 33 are in the Z-axis direction. Then, expansion and contraction are alternately repeated, and flexural vibration in the X-axis direction is generated in the stator 2.

Therefore, when an AC voltage having a phase shifted by 90 degrees is applied from both the first terminal 31t and the second terminal 32t, the flexural vibration in the Y-axis direction and the longitudinal vibration in the Z-axis direction are combined to form the rotor 6. Elliptical vibration in the YZ plane is generated in the step 9 of the stator 2 that comes into contact with the rotor 6, and the rotor 6 rotates about the X axis via frictional force.
Similarly, when an AC voltage having a phase shifted by 90 degrees is applied from both the second terminal 32t and the third terminal 33t, the flexural vibration in the X-axis direction and the vertical vibration in the Z-axis direction are combined to form a rotor. The elliptical vibration in the XZ plane is generated at the step 9 of the stator 2 that comes into contact with the rotor 6, and the rotor 6 rotates about the Y axis through the frictional force.
Further, when an AC voltage having a phase shifted by 90 degrees is applied from both the first terminal 31t and the third terminal 33t, the X axis deflection vibration and the Y axis deflection vibration are combined to form the rotor 6. An elliptical vibration in the XY plane is generated in the step 9 of the stator 2 that comes into contact with the rotor 6, and the rotor 6 rotates about the Z-axis via a frictional force.

As described above, the AC voltage obtained by selecting two terminals among the first terminal 31t, the second terminal 32t, and the third terminal 33t of the vibrator 3 and shifting the phase by 90 degrees from both of these two terminals. Is applied to the stator 2, and as shown by broken arrows in FIG. 5, the in-plane elliptical vibration corresponding to the two selected terminals is formed on the step 9 of the stator 2 in contact with the rotor 6. Will occur.
Here, since the preload acts on the rotor 6 by the urging force of the leaf spring 10 via the corner portion 12 of the preload member 11 and the rotor 6 is pressed against the step 9 of the stator 2, A rotational force is transmitted to the rotor 6 by the frictional force between the step 9.
At this time, the preload member 11 vibrates in a vibration mode different from the vibration mode of the stator 2 as shown by the solid line arrow in FIG. 5 due to the leaf spring 10 interposed between the preload member 11 and the stator 2. The friction loss caused by the contact between the 11 corners 12 and the surface of the rotor 6 is greatly reduced, and the rotor 6 rotates with high torque.

Further, since the preload member 11 is connected to the stator 2 through the leaf spring 10 and vibrates the preload member 11 using the vibration of the stator 2 by the vibrator 3, an ultrasonic motor having a simple configuration can be obtained. .
Further, when the vibrator 3 is stopped and the preload member 11 does not vibrate, the friction force between the corner portion 12 of the preload member 11 and the surface of the rotor 6 increases, whereby the rotor 6 can be held.

  Therefore, by attaching an arm, an imaging device, etc. (not shown) to the surface portion of the rotor 6 exposed through the ring-shaped preload member 11, it is possible to realize a multi-degree-of-freedom actuator, a camera for a wide visual field range, and the like. .

  In addition, the corner | angular part 12 of the ring-shaped preload member 11 does not contact the rotor 6 over the whole periphery, but as shown in FIG. It can also be configured to contact. By doing so, friction loss due to contact between the preload member 11 and the rotor 6 is further reduced, and higher torque can be realized. In this case, it is preferable that the plurality of contact points C of the preload member 11 that contacts the surface of the rotor 6 are symmetrical with respect to the rotor 6.

Embodiment 2. FIG.
FIG. 7 shows an ultrasonic motor according to Embodiment 2 of the present invention. This ultrasonic motor is the same as the ultrasonic motor according to the first embodiment shown in FIG. 1, except that an annular contact member 13 positioned on the XY plane is attached to the inner peripheral edge of the ring-shaped preload member 11. . The contact member 13 is made of a low friction material such as Teflon (registered trademark), and the rotor 6 is held in contact with both the corner 14 formed by the contact member 13 and the step 9 of the stator 2 so as to be rotatable. It is supported by.
Since preload is applied to the rotor 6 via the contact member 13 formed of a low friction material, friction loss due to contact between the contact member 13 and the rotor 6 is further reduced, and a high torque ultrasonic motor is realized. The

Embodiment 3 FIG.
FIG. 8 shows an ultrasonic motor according to Embodiment 3 of the present invention. This ultrasonic motor is the same as the ultrasonic motor according to the first embodiment shown in FIG. 1 except that the preload member 11 is elastically connected to the stator 2 via the leaf spring 10 in the Z-axis direction from the stator 15. The preload member 16 is arranged so as to be separated. A holding member 18 is connected to the preload member 16 via a vibrator 17, and a spring or the like (not shown) is used to bias the holding member 18 toward the stator 15 with respect to the stator 15 or the base block 1. Elastically supported.
The preload member 16, the vibrator 17, and the holding member 18 are all formed in a ring shape having an opening at the center, and the rotor 6 is exposed through these openings. In addition, an annular corner portion 19 located on the XY plane is formed on the inner peripheral edge of the preload member 16.

  As shown in FIG. 9, the vibrator 17 has a structure in which an electrode plate 17a, a piezoelectric element plate 17b, and an electrode plate 17c are sequentially stacked. The piezoelectric element plate 17b is polarized so as to perform deformation behavior such as expansion or contraction in the thickness direction, and the vibrator 17 can be driven and controlled by applying an AC voltage between the electrode plates 17a and 17c. It is configured to be able to. Insulating sheets 20 and 21 are respectively disposed on both surfaces of the vibrator 17, and the vibrator 17 is disposed in a state of being insulated from the preload member 16 and the holding member 18 through the insulating sheets 20 and 21.

  The stator 15 is connected to each other by the connecting bolt 4 in a state where the vibrator 3 is sandwiched between the stator 15 and the base block 1 in the same manner as the stator 2 in the first embodiment, and is in contact with the vibrator 3 of the stator 15. A concave portion 22 having an inner diameter smaller than the diameter of the rotor 6 is formed on the side opposite to the surface. An annular corner 23 located on the XY plane is formed at the periphery of the opening end of the recess 22, and the rotor 6 is in contact with both the corner 23 of the stator 15 and the corner 19 of the preloading member 16. And is held rotatably.

  Even in such a configuration, two terminals are selected from the first terminal 31t, the second terminal 32t, and the third terminal 33t of the vibrator 3, and the phase is shifted by 90 degrees from both of these two terminals. When each of the AC voltages is applied, vibration is generated in the stator 15, and in-plane elliptical vibration corresponding to the selected two terminals is generated in the corner portion 23 of the stator 15 that is in contact with the rotor 6.

At this time, the holding member 18 is biased in the direction of the stator 15 by a spring or the like (not shown), preload is applied to the rotor 6 via the corner portion 19 of the preload member 16, and the rotor 6 is against the corner portion 23 of the stator 15. Therefore, the rotational force is transmitted to the rotor 6 by the frictional force between the rotor 6 and the corner portion 23.
Here, when the vibrator 17 is driven and controlled, the preload member 16 vibrates independently of the vibration of the stator 15 caused by the vibrator 3, thereby causing contact between the corner portion 19 of the preload member 16 and the surface of the rotor 6. The friction loss is greatly reduced, and the rotor 6 rotates with high torque.

  As shown in FIG. 10, if the preloading member 16 and the holding member 18 are supported by the fixture 24 at the node positions formed when the preloading member 16 and the holding member 18 are vibrated by the vibrator 17, the preloading member 16. It is possible to support the preload member 16 while minimizing the influence on the vibration.

Embodiment 4 FIG.
FIG. 11 shows an ultrasonic motor according to Embodiment 4 of the present invention. This ultrasonic motor is the same as the ultrasonic motor according to the third embodiment shown in FIG. 8, except that an annular contact member 25 located on the XY plane is attached to the inner peripheral edge of the ring-shaped preload member 16. . The contact member 25 is made of a low friction material such as Teflon (registered trademark), and the rotor 6 is held in contact with and held by both the corner portion 26 formed by the contact member 25 and the corner portion 23 of the stator 15. It is supported freely.
Since the preload is applied to the rotor 6 via the contact member 25 formed of a low friction material, friction loss due to contact between the contact member 25 and the rotor 6 is further reduced, and a high torque ultrasonic motor is realized. The

  In the first to fourth embodiments described above, the multi-degree-of-freedom ultrasonic motor has been described in which the rotor 6 has a spherical shape, and the stators 2 and 15 are vibrated by the vibrator 3 to rotate the rotor 6 around a plurality of axes. However, the present invention is not limited to this, and the present invention can also be applied to a one-degree-of-freedom ultrasonic motor that rotates a rotor around a single axis.

In the above embodiment, the phase of the alternating voltage applied by selecting two of the first terminal 31t, the second 32t, and the third 33t of the vibrator 3 is shifted by 90 degrees. You may change not only 90 degree | times. Moreover, you may change the voltage value of the alternating voltage to apply. The elliptical vibration generated in the stators 2 and 15 can be controlled by variously controlling the AC voltage.
Further, in the above-described embodiment, the contact between the stators 2 and 15 and the rotor 6 is a corner portion such as the step 9 or the corner portion 23, but is not limited to this configuration. If the elliptical motion can be transmitted, the contact may be made on a flat surface, the contact may be made on a curved surface, or may not be annular.

In the above embodiment, the vibrator 3 uses vibrators that generate longitudinal vibrations in the Z direction and flexural vibrations in the X and Y directions as vibrations in three different directions. It is not necessary. In addition, the vibrator that generates vibrations in the three directions uses the first piezoelectric element portion 31, the second piezoelectric element portion 32, and the third piezoelectric element portion 33 and piezoelectric elements corresponding to the respective directions. In order to generate vibration, vibrations from a plurality of piezoelectric element units may be combined, or one piezoelectric element unit is polarized into three or more to generate vibrations in two or more directions in one piezoelectric element unit. You may let them.
In the above embodiment, two of the three directions are selected to generate vibration. However, an AC voltage is applied to all the piezoelectric elements corresponding to the three directions, and the phase and amplitude of vibration in each direction are adjusted. A synthetic vibration may be generated by controlling.

It is sectional drawing which shows the ultrasonic motor which concerns on Embodiment 1 of this invention. 1 is a plan view showing an ultrasonic motor according to Embodiment 1. FIG. 3 is a partial cross-sectional view showing a configuration of a vibrator used in Embodiment 1. FIG. 3 is a perspective view showing polarization directions of three pairs of piezoelectric element plates of the vibrator used in Embodiment 1. FIG. 2 is a partial enlarged cross-sectional view of the ultrasonic motor according to Embodiment 1. FIG. FIG. 6 is a plan sectional view showing the shape of a preload member in a modification of the first embodiment. 5 is a cross-sectional view showing an ultrasonic motor according to Embodiment 2. FIG. 6 is a cross-sectional view showing an ultrasonic motor according to Embodiment 3. FIG. 6 is a partial cross-sectional view illustrating a configuration of a vibrator used in Embodiment 3. FIG. 10 is a plan view showing an ultrasonic motor according to a modification of the third embodiment. FIG. FIG. 6 is a cross-sectional view showing an ultrasonic motor according to a fourth embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Base block, 2,15 Stator, 3,17 Vibrator, 4 Connection bolt, 5,22 Recessed part, 6 Rotor, 7 Small diameter part, 8 Large diameter part, 9 Step, 10 Leaf spring, 11,16 Preload member, 12 , 14, 19, 23, 26 Corner portion, 13, 25 Contact member, 18 Holding member, 20, 21, 34 to 37 Insulating sheet, 24 Fixing tool, 31 First piezoelectric element portion, 32 Second piezoelectric element Part, 33 third piezoelectric element part, 17a, 17c, 31a, 31c, 31e, 32a, 32c, 32e, 33a, 33c, 33e electrode plate, 17b, 31b, 31d, 32b, 32d, 33b, 33d, piezoelectric element Plate, 31t 1st terminal, 32t 2nd terminal, 33t 3rd terminal, C contact location.

Claims (12)

A stator,
A rotor contacted and supported by the stator;
Stator vibration means for rotating the rotor by vibrating the stator;
A preload member arranged in contact with the surface of the rotor at least when stopped;
An ultrasonic motor comprising: a preload member vibrating means for preloading the rotor with respect to the stator by vibrating the preload member.   The ultrasonic motor according to claim 1, wherein the preload member vibrating means preloads the rotor with respect to the stator by vibrating the preload member in a vibration mode different from a vibration mode of the stator. The preload member is elastically supported by the stator;
The ultrasonic motor according to claim 1, wherein the stator vibration unit also serves as the preload member vibration unit.   The ultrasonic motor according to claim 3, wherein the preload member is supported by the stator via a spring. The preload member is spaced apart from the stator;
The ultrasonic motor according to claim 1, wherein the preload member vibration means includes a piezoelectric element plate attached to the preload member.   The ultrasonic motor according to claim 5, wherein the preload member is supported at a node position formed when vibrating by the piezoelectric element plate. The rotor is substantially spherical,
The ultrasonic motor according to claim 1, wherein the stator vibration unit vibrates the stator to rotate the rotor around a plurality of axes.   The ultrasonic motor according to claim 7, wherein the preload member has a ring shape arranged so as to surround the rotor in an annular shape along a circumferential direction thereof.   The ultrasonic motor according to claim 7 or 8, wherein the preload member has an abutting member made of a low friction material at a portion in contact with the surface of the rotor.   The ultrasonic motor according to any one of claims 7 to 9, wherein the stator contacts the surface of the rotor only at a plurality of locations in a circumferential direction.   The ultrasonic motor according to claim 10, wherein the plurality of locations are symmetrical with respect to the rotor.   The stator vibration means has three pairs of piezoelectric element plates that generate vibrations in three different directions, and generates a combined vibration in which at least two of the three directions of vibration are combined with their phases shifted from each other. The ultrasonic motor according to claim 7, wherein an elliptical motion is formed in a contact portion of the stator with the rotor.

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